5 research outputs found
Crystallization and sinterability of lanthanum-strontium-borate-glass powders
Predmet ove doktorske disertacije je ispitvanje kristalizacionog ponašanja i sinterabilnosti
boratnih stakala iz sistema La2O3-SrO-B2O3, o čemu postoji ograničen broj podataka u
literaturi.
Preliminarna ispitivanja su obuhvatala dobijanje 4 različita sastava ovog sistema, tako što
se sadržaj lantana povećavao na račun stroncijuma, dok je sadržaj bora bio konstantan:
5,7La2O3·22,9SrO·71,4B2O3; 9,5La2O3·19,1SrO·71,4B2O3;
14,3La2O3·14,3SrO·71,4B2O3 i 19,1La2O3·9,5SrO·71,4B2O3. Isptivana su fizička i
strukturna svojstva kao i kristalizacione karakteristike i sinterabilnost. Kristalizaciono
ponašanje stakala praćeno je diferencijalnom termijskom analizom (DTA), rendgenskom
difrakcijom praha (XRD), transmisionim i skenirajućim elektronskim mikroskopima (TEM
i SEM), dok je sinterabilnost prahova praćena primenom termomikroskopa (TM) i DTA.
Rendgenskom difrakcijom praha identifikovane su faze nastale tokom toplotne obrade,
odnosno nakon kristalizacije, dok je mehanizam kristalizacije, kao i mikrostruktura stakla
nakon toplotne obrade ispitivana SEM-om.
Rezultati početnih ispitivanja ukazali su da staklo 14,3La2O3·14,3SrO·71,4B2O3 pokazuje
niz specifičnosti u pogledu kristalizacionih karakteristika, kao i sinterabilnosti. Na osnovu
rezultata XRD, TEM i SEM analize utvrđen je površinski mehanizam rasta kristalne faze
koja je istog sastava kao i staklo (polimorfna kristalizacija). Za ovu fazu u literaturi ne
postoje podaci, tako da su na osnovu TEM i XRD analize dobijeni podaci za jediničnu
ćeliju.
U cilju dobijanja što boljih rezultata sinterovanja pripremljen je prah stakla izuzetno malih
veličina čestica. Proces sinterovanja, odnosno, sinter-kristalizacije praćen je korišćenjem
DTA, TM i optičkog dilatometra. Ispitivan je uticaj temperature sinterovanja, kao i brzine
zagrevanja do izabrane temperature sinterovanja na efikasnost sinterovanja. Stepen
denzifikacije, uzoraka je određen merenjem poroznosti nakon toplotne obrade. Za
identifikaciju faza koje su nastale u sinterovanim uzorcima korišćena je XRD tehnika.
Sinterovani uzorci su analizirani skenirajućim elektronskim mikroskopom, primenom
detektora sekundarnih elektrona, SE, i povratno rasejanih elektrona, BSE, da bi se stekao
uvid u poroznost i u mikrostrukturu nastale staklo-keramike...The subject of this doctoral thesis is the study of the crystallization behavior and the
sinterability of the borate glasses system La2O3-B2O3-SrO. In literature there are limited
data from the crystallization characteristics and sinterability of these glasses. Preliminary
goal of this study was to investigate 4 different composition of the system, in which the
content lanthanum of was increased at the expense of the strontium, while the boron
content remained unchanged: 5,7La2O3·22,9SrO·71,4B2O3; 9,5La2O3·19,1SrO·71,4B2O3;
14,3La2O3·14,3SrO·71,4B2O3 and 19,1La2O3·9,5SrO·71,4B2O3. Physical and the
structural properties as well as the crystallization characteristics and sinterability of glasses
were investigated. Crystallization behavior was studied by the differentially thermal
analysis (DTA), X-ray diffraction (XRD), transmission and scanning electron microscopy
(TEM and SEM), while the sinterability by the hot stage microscopy (HSM) and DTA. For
the identification of the crystalline phases after thermal treatment (after the crystallization)
XRD was used. Mechanism of the crystallization and the resulting phase microstructure
were observed by SEM. The results of the preliminary investigations revealed that the glass
14,3La2O3·14,3SrO·71,4B2O3 shows the specific crystallization and sinterabilty
characteristics. Based on XRD, TEM and SEM results the surface crystallization
mechanisam was detected, where the obtained crystalline phase was of the same
composition as the initial glass (polymorphic crystallization). In the literature there are no
data for this crystalline phase, so XRD and TEM were used for the determination of the
unit cell parameters.
In order to obtain the best possible sintering results, the glass powder of extremely small
particles (nanoparticles) was prepared. The sintering process was followed by the DTA,
HSM and the contactless optical dilatometer. The effects of the sintering temperature, as
well as the heating rate up to sintering temperatures, on the sintering efficiency were
investigated. The quality of sintering, densification of the samples, was evaluated by the
measuring the porosity of samples after the thermal treatment. XRD was used to determine
the composition of the phase resulting from sintering. The sintered samples were analysed
by SEM, equipped with secondary electron (SE) and backscattered electron detectors
(BSE), to gain insight in the porosity and the microstructure of the obtained glass-ceramic..
Crystallization and sinterability of lanthanum-strontium-borate-glass powders
Predmet ove doktorske disertacije je ispitvanje kristalizacionog ponašanja i sinterabilnosti
boratnih stakala iz sistema La2O3-SrO-B2O3, o čemu postoji ograničen broj podataka u
literaturi.
Preliminarna ispitivanja su obuhvatala dobijanje 4 različita sastava ovog sistema, tako što
se sadržaj lantana povećavao na račun stroncijuma, dok je sadržaj bora bio konstantan:
5,7La2O3·22,9SrO·71,4B2O3; 9,5La2O3·19,1SrO·71,4B2O3;
14,3La2O3·14,3SrO·71,4B2O3 i 19,1La2O3·9,5SrO·71,4B2O3. Isptivana su fizička i
strukturna svojstva kao i kristalizacione karakteristike i sinterabilnost. Kristalizaciono
ponašanje stakala praćeno je diferencijalnom termijskom analizom (DTA), rendgenskom
difrakcijom praha (XRD), transmisionim i skenirajućim elektronskim mikroskopima (TEM
i SEM), dok je sinterabilnost prahova praćena primenom termomikroskopa (TM) i DTA.
Rendgenskom difrakcijom praha identifikovane su faze nastale tokom toplotne obrade,
odnosno nakon kristalizacije, dok je mehanizam kristalizacije, kao i mikrostruktura stakla
nakon toplotne obrade ispitivana SEM-om.
Rezultati početnih ispitivanja ukazali su da staklo 14,3La2O3·14,3SrO·71,4B2O3 pokazuje
niz specifičnosti u pogledu kristalizacionih karakteristika, kao i sinterabilnosti. Na osnovu
rezultata XRD, TEM i SEM analize utvrđen je površinski mehanizam rasta kristalne faze
koja je istog sastava kao i staklo (polimorfna kristalizacija). Za ovu fazu u literaturi ne
postoje podaci, tako da su na osnovu TEM i XRD analize dobijeni podaci za jediničnu
ćeliju.
U cilju dobijanja što boljih rezultata sinterovanja pripremljen je prah stakla izuzetno malih
veličina čestica. Proces sinterovanja, odnosno, sinter-kristalizacije praćen je korišćenjem
DTA, TM i optičkog dilatometra. Ispitivan je uticaj temperature sinterovanja, kao i brzine
zagrevanja do izabrane temperature sinterovanja na efikasnost sinterovanja. Stepen
denzifikacije, uzoraka je određen merenjem poroznosti nakon toplotne obrade. Za
identifikaciju faza koje su nastale u sinterovanim uzorcima korišćena je XRD tehnika.
Sinterovani uzorci su analizirani skenirajućim elektronskim mikroskopom, primenom
detektora sekundarnih elektrona, SE, i povratno rasejanih elektrona, BSE, da bi se stekao
uvid u poroznost i u mikrostrukturu nastale staklo-keramike...The subject of this doctoral thesis is the study of the crystallization behavior and the
sinterability of the borate glasses system La2O3-B2O3-SrO. In literature there are limited
data from the crystallization characteristics and sinterability of these glasses. Preliminary
goal of this study was to investigate 4 different composition of the system, in which the
content lanthanum of was increased at the expense of the strontium, while the boron
content remained unchanged: 5,7La2O3·22,9SrO·71,4B2O3; 9,5La2O3·19,1SrO·71,4B2O3;
14,3La2O3·14,3SrO·71,4B2O3 and 19,1La2O3·9,5SrO·71,4B2O3. Physical and the
structural properties as well as the crystallization characteristics and sinterability of glasses
were investigated. Crystallization behavior was studied by the differentially thermal
analysis (DTA), X-ray diffraction (XRD), transmission and scanning electron microscopy
(TEM and SEM), while the sinterability by the hot stage microscopy (HSM) and DTA. For
the identification of the crystalline phases after thermal treatment (after the crystallization)
XRD was used. Mechanism of the crystallization and the resulting phase microstructure
were observed by SEM. The results of the preliminary investigations revealed that the glass
14,3La2O3·14,3SrO·71,4B2O3 shows the specific crystallization and sinterabilty
characteristics. Based on XRD, TEM and SEM results the surface crystallization
mechanisam was detected, where the obtained crystalline phase was of the same
composition as the initial glass (polymorphic crystallization). In the literature there are no
data for this crystalline phase, so XRD and TEM were used for the determination of the
unit cell parameters.
In order to obtain the best possible sintering results, the glass powder of extremely small
particles (nanoparticles) was prepared. The sintering process was followed by the DTA,
HSM and the contactless optical dilatometer. The effects of the sintering temperature, as
well as the heating rate up to sintering temperatures, on the sintering efficiency were
investigated. The quality of sintering, densification of the samples, was evaluated by the
measuring the porosity of samples after the thermal treatment. XRD was used to determine
the composition of the phase resulting from sintering. The sintered samples were analysed
by SEM, equipped with secondary electron (SE) and backscattered electron detectors
(BSE), to gain insight in the porosity and the microstructure of the obtained glass-ceramic..
Crystal growth of la(2)srb(10)o(19)from undercooled melt
The crystal growth rate of La(2)SrB(10)O(19)in an undercooled melt of stoichiometric composition was studied. The crystallization of the bulk samples was performed in a single-stage regime under isothermal conditions at the selected temperatures for the different time periods. The surface crystallization was observed and in all crystallized samples, the La(2)SrB(10)O(19)crystalline phase was identified. Based on the dependence of the crystalline layer thickness on treatment time at selected temperature, crystal growth rate was obtained. The crystal growth rates were from 1.65 x 10(-8)to 2.77 x 10(-7)m s(-1)in the temperature interval (700-780 degrees C). The experimental values were compared to the calculated values using theoretical model of the crystal growth. The experimental growth rate followed the same trend as the calculated growth rate, but the experimental values were higher than the calculated